A zig-zag classifier is adapted to separate supplied material to be separated in the classifier into a coarse and a fine fraction. It has shown that it is to be aspired for the surface of the classifier channel to have the following ratio: length/width≦4. The angle of the teeth of the zig-zag classifier ideally lies in the region of 120°.
The material to be separated is supplied via a supply device being sealed against the environment into the zig-zag classifier and is distributed across the entire cross-section of the classifier channel. The classifying air generated by the fan flows through the classifier from the bottom to the top, while it is blown through the material to be separated and separates it. As a result of the multiply angled classifier channel, the material to be separated is forced to perform a zig-zag-like motion. At each bend of the classifier channel, the material to be separated must traverse the air stream and then impact the oppositely disposed classifier wall. Air is blown preferably transversely against the constituents of the material to be separated when they change from one channel side to the other and thereby deflects them to a varying degree. In this, heavier constituents drop down into the classifier channel due to the force of gravity. The lighter constituents are carried upwardly by the upwardly directed airflow.
Good separation of lighter and heavier constituents is achieved due to the multiple directional changes in the classifier channel. The dimensions of the classifier channel as well as the speed of the classifying air and the load of material to be separated can vary depending on the materials and the performance. The spacing of the Z-shaped plates in the classifier channel creates a certain flow, where the spacing of the classifier channel for a particular material is approximately uniform. For larger throughputs, the classifier channel is therefore increased in depth so that transferring the material in and out through cellular wheel sluices becomes increasingly difficult.